Automatic machine for manufacturing and filling packs, such as machines for manufacturing mesh bags containing horticultural products, in which the packing operations are carried out automatically and in which successive filled packs are conveyed, suspended from conveyor means, from a last station in which the pack is handled for its closure to a delivery ramp, on which the held packs are released by said conveyor means, are known today. In the example described in patent EP1481899, the conveyor means consist of a pair of arms describing an alternating movement, which close to hold the successive filled packs in the closing station and which move towards the ramp until reaching the end of their path, in which they open to release the pack before moving in the opposite direction until reaching the closing station to hold another filled pack, and so on and so forth.
A drawback of packaging in automatic machines such as the one described in patent document EP1481899, which has a high cyclic rate, is the control of the weighing of the filled and closed bags.
Preferably, the weighing must be done with the pack suspended, so the weighing of the filled packs deposited on conveyor belts or the like provided with weight sensors, and especially when the packs are formed by flexible bags containing horticultural products, such as tubers and citrus fruits, it is not altogether satisfactory due to the little stability of the bags and of their content, even more when the conveyor belt is in motion, being able to cause a redistribution of the products in the pack which can alter the measurement of the weight.
If one wants to avoid altering or modifying the existing machines, the weighing of suspended packs means that the filled packs must be transferred from the conveyor means of the machine to a weighing device. The measurement of the weight of the filled packs on static weighing means involves a deceleration of the forward movement of the packs, which generates unwanted inertias that can alter the measurement, and a reduction of the production volume due to the stabilization time required by the weight measurement means when the load to be measured is varied significantly.
The patent document ES 2212693 describes a solution that can be applied to automatic machines, comprising first and second filled pack conveyor means, both provided with several pairs of conveyor arms separated by a predetermined distance, the pairs of conveyor arms being assembled in guides describing a straight path and a closed path, respectively, which move at the same speed and such that the packs can be transferred without stopping from the pairs of arms of the first conveyor means to the pairs of arms of the second conveyor means. The guide of the second conveyor means is provided with a straight weighing section in which weighing means are arranged.
This solution has certain drawbacks, among which its high cost due to incorporating a high number of pairs of arms, the complexity in operating the pairs of arms when transferring the packs from some pairs of arms to others, and the scarce length of the weighing section required for the individual measurement of the filled packs, which cannot be greater than the distance which separates two consecutive pairs of arms, standing out among them. In addition to the aforementioned drawbacks, it should be added that it is a solution that cannot be easily applied to a machine such as the one described in patent document EP1481899, and which leads to an installation that is not at all compact and occupies a lot of space.
An object of the present invention is to describe a process for the weighing of the filled packs which solves the aforementioned drawbacks, as well as a device for putting the process into practice, which device is furthermore more compact, cost-effective and versatile than the devices known to date.